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RSS2004 Vol. 16, No. 07
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2004,
16.
Abstract:
Based on silicon micromachining technology, a novel deformable mirror with 30mm×30mm effective reflecting surface and 49 actuators is designed and fabricated. It is composed of a silicon membrane, at the back of which is attached by a 7×7 pillars array. The pillars and bonding part are fabricated through two etching steps with different depth. In terms of optimization, a strip pattern is designed specially for the convex corner compensation during the etching process, and the anodic bonding process is performed under 0.2MPa atmospheric pressures.
Based on silicon micromachining technology, a novel deformable mirror with 30mm×30mm effective reflecting surface and 49 actuators is designed and fabricated. It is composed of a silicon membrane, at the back of which is attached by a 7×7 pillars array. The pillars and bonding part are fabricated through two etching steps with different depth. In terms of optimization, a strip pattern is designed specially for the convex corner compensation during the etching process, and the anodic bonding process is performed under 0.2MPa atmospheric pressures.
2004,
16.
Abstract:
In this paper, a software-package, DISORT (discrete ordinate method), is used to compute the object-background contrast at 0.55μm wavelength under the standard atmosphere. It is also analyzed that object-background contrast is affected by many factors, including the horizontal visibility, altitude, the visual zenith angle, and solar zenith angle, azimuthal angles difference between the observer and the sun, and the aerosol single scattering albedo. As the result, the contrast increases with the increase of the observer zenith angle, with the decrease of the solar zenith angle, with the increase of the azimuthal angles difference, with the decrease of the altitude, and with the decrease of the single scattering albedo.
In this paper, a software-package, DISORT (discrete ordinate method), is used to compute the object-background contrast at 0.55μm wavelength under the standard atmosphere. It is also analyzed that object-background contrast is affected by many factors, including the horizontal visibility, altitude, the visual zenith angle, and solar zenith angle, azimuthal angles difference between the observer and the sun, and the aerosol single scattering albedo. As the result, the contrast increases with the increase of the observer zenith angle, with the decrease of the solar zenith angle, with the increase of the azimuthal angles difference, with the decrease of the altitude, and with the decrease of the single scattering albedo.
2004,
16.
Abstract:
Based on the requirement of laser propelling, this paper illuminates in how to choose the high power laser.The requirements on the laser are: (1) high average power and peak power; (2) high single-pulse energy; (3) high repetition frequency; (4) excellent transmitting property in atmosphere. The paper mainly analyzes the characteristics of YAG laser, free electron laser and TEA CO2 laser, compares their average power, peak power, high single-pulse energy, and transmitting property in atmosphere. The result shows nowadays, TEA CO2 laser is the most appropriate one at present to be used as the high power source in the field.It's power can reach 10kW level, single pulse energy can reach 0.5~1kJ, repetitive frequency is 20~40Hz, the laser wavelength lies in the atmospheric window, and it isn't
Based on the requirement of laser propelling, this paper illuminates in how to choose the high power laser.The requirements on the laser are: (1) high average power and peak power; (2) high single-pulse energy; (3) high repetition frequency; (4) excellent transmitting property in atmosphere. The paper mainly analyzes the characteristics of YAG laser, free electron laser and TEA CO2 laser, compares their average power, peak power, high single-pulse energy, and transmitting property in atmosphere. The result shows nowadays, TEA CO2 laser is the most appropriate one at present to be used as the high power source in the field.It's power can reach 10kW level, single pulse energy can reach 0.5~1kJ, repetitive frequency is 20~40Hz, the laser wavelength lies in the atmospheric window, and it isn't
2004,
16.
Abstract:
Dependence of image contrast on atmospheric back scattering by continuous coaxial illumination is analyzed. As a result, several equations on imaging contrast are given and relation between image contrast and weather is studied. Scattering flux is calculated by Mie scattering theory on condition that relative scale and refractive index of the particles are known. Dependence of image contrast on weather is presented in this paper. Theoretical results accord with experiments and indicate it is impossible to obtain distinct image of target through long path of atmosphere under coaxial continuous illumination when visibility is not very well. So range-gated method is necessary in active imaging system.
Dependence of image contrast on atmospheric back scattering by continuous coaxial illumination is analyzed. As a result, several equations on imaging contrast are given and relation between image contrast and weather is studied. Scattering flux is calculated by Mie scattering theory on condition that relative scale and refractive index of the particles are known. Dependence of image contrast on weather is presented in this paper. Theoretical results accord with experiments and indicate it is impossible to obtain distinct image of target through long path of atmosphere under coaxial continuous illumination when visibility is not very well. So range-gated method is necessary in active imaging system.
2004,
16.
Abstract:
Impulse coupling-coefficient is an important index, which represents the capability of laser energy transforming kinetic energy. Based on the measure displacement method of high-speed photograph technology, using Kalman filtering method, velocity calculated method of lightcraft is proposed for horizontal parallel wire supported laser propulsion. From the proposed testing and calculation method, the problem of velocity random fluctuating phenomenon owing to test data fluctuating is resolved. The presented method can be used in engineering measure and design for calculating impulse coupling-coefficient of laser propulsion.
Impulse coupling-coefficient is an important index, which represents the capability of laser energy transforming kinetic energy. Based on the measure displacement method of high-speed photograph technology, using Kalman filtering method, velocity calculated method of lightcraft is proposed for horizontal parallel wire supported laser propulsion. From the proposed testing and calculation method, the problem of velocity random fluctuating phenomenon owing to test data fluctuating is resolved. The presented method can be used in engineering measure and design for calculating impulse coupling-coefficient of laser propulsion.
2004,
16.
Abstract:
Starting from the propagation equation of complex- argument cosh- Gaussian (ChG) beams passing through a paraxial ABCD optical system and based on the second- order moments method, the closed- form expression for the beam width of complex- argument ChG beams passing through a paraxial ABCD optical system is derived, the waist width and their location of the beams propagating in free space and through a thin lens are also deduced. Numerical calculations are made to illustrate the properties of the complex- argument ChG beams.
Starting from the propagation equation of complex- argument cosh- Gaussian (ChG) beams passing through a paraxial ABCD optical system and based on the second- order moments method, the closed- form expression for the beam width of complex- argument ChG beams passing through a paraxial ABCD optical system is derived, the waist width and their location of the beams propagating in free space and through a thin lens are also deduced. Numerical calculations are made to illustrate the properties of the complex- argument ChG beams.
2004,
16.
Abstract:
In this paper , compensating capabilities of the low frequency aberrations for 37 elements active deformable mirror have been analysed by the finite element method and Algor software. The key parameters are confirmed: mirror thickness 8mm, driver span 46mm and pole diameter 12mm. The simulation analysis shows that the low frequency aberrations of 37 elements active mirror can be corrected effectively. The RMS of the aberrations corrected is nogreater than λ／８. This gives the theoretic evidence for producing the active mirror．
In this paper , compensating capabilities of the low frequency aberrations for 37 elements active deformable mirror have been analysed by the finite element method and Algor software. The key parameters are confirmed: mirror thickness 8mm, driver span 46mm and pole diameter 12mm. The simulation analysis shows that the low frequency aberrations of 37 elements active mirror can be corrected effectively. The RMS of the aberrations corrected is nogreater than λ／８. This gives the theoretic evidence for producing the active mirror．
2004,
16.
Abstract:
Laser scintillation in the turbulent atmosphere was analyzed using the fractal methods, especially its fractal dimension and Hurst exponent. The results show that: the laser scintillation is a nonstationary random process with long-run and positive correlation. In the weak fluctuation conditions (the scintillation index in the range of 0 to 1.2), the fractal dimension would increase and the Hurst exponent would decrease with the increase of the scintillation index. That means the scintillation's intensity and complexity both increase and the temporal correlation decreases as the degree of fluctuation increases. In the strong fluctuation conditions, the limited data may reflect that the fractal dimension keeps on increasing, and no saturation appears. In addition, the effect of the Fresnel
Laser scintillation in the turbulent atmosphere was analyzed using the fractal methods, especially its fractal dimension and Hurst exponent. The results show that: the laser scintillation is a nonstationary random process with long-run and positive correlation. In the weak fluctuation conditions (the scintillation index in the range of 0 to 1.2), the fractal dimension would increase and the Hurst exponent would decrease with the increase of the scintillation index. That means the scintillation's intensity and complexity both increase and the temporal correlation decreases as the degree of fluctuation increases. In the strong fluctuation conditions, the limited data may reflect that the fractal dimension keeps on increasing, and no saturation appears. In addition, the effect of the Fresnel
2004,
16.
Abstract:
Effects of certain impurities, which exit in growth solution of KDP crystal, on optical qualities of KDP crystal were investigated. The results showed that the effects of different kinds of impurities are not the same. The reason can be ascribed to the chemical structure and chemical bonds between the impurities and surface atoms of KDP crystal are not same．Those impurities have similar structure and easy to form H bonds with ［H２PO４］-,such as pyrophosphate and sulfate affect pyramidal sector of KDP crystal easily while the other impurities, such as Cl- have no evident effect on the growth and properties of KDP crystals.
Effects of certain impurities, which exit in growth solution of KDP crystal, on optical qualities of KDP crystal were investigated. The results showed that the effects of different kinds of impurities are not the same. The reason can be ascribed to the chemical structure and chemical bonds between the impurities and surface atoms of KDP crystal are not same．Those impurities have similar structure and easy to form H bonds with ［H２PO４］-,such as pyrophosphate and sulfate affect pyramidal sector of KDP crystal easily while the other impurities, such as Cl- have no evident effect on the growth and properties of KDP crystals.
2004,
16.
Abstract:
Beam-converting annular resonator(BCAR) possesses outstanding caracteristics of high extraction efficiency and near-diffractive beam quality.But the numerical simulation of BCAR is a hard work,for the thin annular beam propagating calculation will cost much computer work with conventional methods.In this paper a clever finite difference method based on coordinates transform is presented.This method can largely reduce the time for calculating annular beam propagation,it also has higher precision than W.D.Murphy's approximation method does．
Beam-converting annular resonator(BCAR) possesses outstanding caracteristics of high extraction efficiency and near-diffractive beam quality.But the numerical simulation of BCAR is a hard work,for the thin annular beam propagating calculation will cost much computer work with conventional methods.In this paper a clever finite difference method based on coordinates transform is presented.This method can largely reduce the time for calculating annular beam propagation,it also has higher precision than W.D.Murphy's approximation method does．
2004,
16.
Abstract:
The thermal resistance of copper micro-channels cooler was analyzed, and a stackable copper micro-channels cooler with five layers was designed in this paper. The line cutting is adoted in the cooler process, the channel of each layer is 0.2mm wide and 0.3mm deep, the layers are assembled with vacuum solder, the thermal resistance of the cooler for DL with the cavity length of 0.6mm and width of 10mm is measured as 0.58℃/W. It was proved by experiment that the cooler was suitable for DL package with 10% duty cycle work．
The thermal resistance of copper micro-channels cooler was analyzed, and a stackable copper micro-channels cooler with five layers was designed in this paper. The line cutting is adoted in the cooler process, the channel of each layer is 0.2mm wide and 0.3mm deep, the layers are assembled with vacuum solder, the thermal resistance of the cooler for DL with the cavity length of 0.6mm and width of 10mm is measured as 0.58℃/W. It was proved by experiment that the cooler was suitable for DL package with 10% duty cycle work．
2004,
16.
Abstract:
Experiment system to measure the damage thresholds of K9 glass irradiated by ns pulsed laser is established. Strong attention is paid to the method to detect the precusor of the damage. The sharp decrease of transmissivity or generation of scattered light are assumed to be the damage precursor, and thereby damage threshold is measured to be 18mJ or 1015W/m2, and the dependence of transmissivity on incident energy is presented. From the experiment result, it is found that avalanche ionization and self-focusing effect dominate the damage process in transparent dielectric.
Experiment system to measure the damage thresholds of K9 glass irradiated by ns pulsed laser is established. Strong attention is paid to the method to detect the precusor of the damage. The sharp decrease of transmissivity or generation of scattered light are assumed to be the damage precursor, and thereby damage threshold is measured to be 18mJ or 1015W/m2, and the dependence of transmissivity on incident energy is presented. From the experiment result, it is found that avalanche ionization and self-focusing effect dominate the damage process in transparent dielectric.
2004,
16.
Abstract:
The basic target used in many inertial confinement fusion(ICF) experiments is a hollow microsphere of glass or plastic. Generally, the hollow plastic microsphere is composed of three layers: polystyrene(PS), polyvinyl alcohol(PVA) and carbon hydrogen(CH).This paper focuses on the filling-gas temperature effects on the PS-PVA-CH hollow plastic microsphere properties such as the shell strength and the surface quality. Experiments show that although the material of PS and PVA has high decomposed temperature the strength decreases rapidly as the temperature increases. The PS-PVA shell strength is not enough for Ar-filling. After coating the CH ablator the microsphere can be filled with Ar at 110℃.
The basic target used in many inertial confinement fusion(ICF) experiments is a hollow microsphere of glass or plastic. Generally, the hollow plastic microsphere is composed of three layers: polystyrene(PS), polyvinyl alcohol(PVA) and carbon hydrogen(CH).This paper focuses on the filling-gas temperature effects on the PS-PVA-CH hollow plastic microsphere properties such as the shell strength and the surface quality. Experiments show that although the material of PS and PVA has high decomposed temperature the strength decreases rapidly as the temperature increases. The PS-PVA shell strength is not enough for Ar-filling. After coating the CH ablator the microsphere can be filled with Ar at 110℃.
2004,
16.
Abstract:
In the test process of the large aperture components the influence of the tilting of the components is very serious. Specially, in the sub-aperture stitching process the tilting of the components may cause the missing of the data. This paper introduces the anti-tilting technology, which tilts the interferogram on the opposite direction of the components' tilting. To avoid the difficulty of manual operation, the computer optimization method has been employed. Experiments have been done to verify the feasibility and the validity of this technique. After the anti-titling the right stitching result can be gotten and it is possible to compare different test results with one test system. And the mean of the residual errors of the compare is only ０．１２λ (λ equals to 633nm).
In the test process of the large aperture components the influence of the tilting of the components is very serious. Specially, in the sub-aperture stitching process the tilting of the components may cause the missing of the data. This paper introduces the anti-tilting technology, which tilts the interferogram on the opposite direction of the components' tilting. To avoid the difficulty of manual operation, the computer optimization method has been employed. Experiments have been done to verify the feasibility and the validity of this technique. After the anti-titling the right stitching result can be gotten and it is possible to compare different test results with one test system. And the mean of the residual errors of the compare is only ０．１２λ (λ equals to 633nm).
2004,
16.
Abstract:
Proton emission patterns from the rear surface of targets irradiated by 60fs laser pulse at different intensity have been studied. The filaments of protons emission from 20μm Cu target were observed in the shots with lower laser intensity (about 2×1017W/cm2). As the laser intensity increased up to about 1×1018W/cm2 for the same target thickness, the filaments of proton beam disappeared and a hollow proton beam emerged. The patterns of proton beams revealed the traverse distribution of hot electrons reached the rear surface of target after a long distance transportation from the front surface of target. In this process, Weibel instability will drive electron beam into hollow structure and break into filaments in the end.
Proton emission patterns from the rear surface of targets irradiated by 60fs laser pulse at different intensity have been studied. The filaments of protons emission from 20μm Cu target were observed in the shots with lower laser intensity (about 2×1017W/cm2). As the laser intensity increased up to about 1×1018W/cm2 for the same target thickness, the filaments of proton beam disappeared and a hollow proton beam emerged. The patterns of proton beams revealed the traverse distribution of hot electrons reached the rear surface of target after a long distance transportation from the front surface of target. In this process, Weibel instability will drive electron beam into hollow structure and break into filaments in the end.
2004,
16.
Abstract:
The coupled wave theory of nonlinear optics and continuous equations of hydromechanics are adopted to establish two-dimensional theoretical model of seeded and narrowband pumped transverse SBS. Based on these equations, investigations of the effect of broadband pump on Stokes gain are presented by numerical simulations. The investigation shows that the SBS gain will decrease significantly if laser bandwidth are a little greater than the SBS linewidth. Greater the bandwidth, less the Stokes gain. The bad effects induced by transverse SBS can be suppressed when the bandwidth is greater than 20GHz. On the other hand, modulation frequency will influence Stokes gain and the optimal frequency through the numerical simulations can be chosen.
The coupled wave theory of nonlinear optics and continuous equations of hydromechanics are adopted to establish two-dimensional theoretical model of seeded and narrowband pumped transverse SBS. Based on these equations, investigations of the effect of broadband pump on Stokes gain are presented by numerical simulations. The investigation shows that the SBS gain will decrease significantly if laser bandwidth are a little greater than the SBS linewidth. Greater the bandwidth, less the Stokes gain. The bad effects induced by transverse SBS can be suppressed when the bandwidth is greater than 20GHz. On the other hand, modulation frequency will influence Stokes gain and the optimal frequency through the numerical simulations can be chosen.
2004,
16.
Abstract:
A physical model of partially ionized high-Z atoms in an intense laser field is presented, in which a spheroid distribution for the electron cloud (bound electron) surrounding the nucleus is assumed. The first and the third susceptibilities, as well as the nonlinear polarization current and the refractive index, are analytically obtained by this model. At low laser field limit, these results are consistent with that obtained from the traditional non-harmonic oscillator model, nay, the corresponding characteristic frequency of oscillator and the nonlinear coefficient can be found self-consistently from the presented model.
A physical model of partially ionized high-Z atoms in an intense laser field is presented, in which a spheroid distribution for the electron cloud (bound electron) surrounding the nucleus is assumed. The first and the third susceptibilities, as well as the nonlinear polarization current and the refractive index, are analytically obtained by this model. At low laser field limit, these results are consistent with that obtained from the traditional non-harmonic oscillator model, nay, the corresponding characteristic frequency of oscillator and the nonlinear coefficient can be found self-consistently from the presented model.
2004,
16.
Abstract:
The paper brings forward a serial network model of the mismatches in traveling wave tube (TWT) based on the physical phenomenon that microwave signal reflects between the two microwave mismatches at the output termination and attenuator of TWT. The effect of the two mismatches on the phase coincidence and amplitude coincidence of TWT is analyzed. The analysis indicates that the mismatches can lead to the possibility that the phase of phase coincidence TWT can't be compensated. It is necessary to measure the two mismatehes of TWT and combine with the production technique so as to reduce the reflections and improve the production quality of phase coincidence TWT.
The paper brings forward a serial network model of the mismatches in traveling wave tube (TWT) based on the physical phenomenon that microwave signal reflects between the two microwave mismatches at the output termination and attenuator of TWT. The effect of the two mismatches on the phase coincidence and amplitude coincidence of TWT is analyzed. The analysis indicates that the mismatches can lead to the possibility that the phase of phase coincidence TWT can't be compensated. It is necessary to measure the two mismatehes of TWT and combine with the production technique so as to reduce the reflections and improve the production quality of phase coincidence TWT.
2004,
16.
Abstract:
The influence of uniform magnetic field or PPM(periodic permanent magnetic) field on suppressing BWO(back-wave oscillation) is analyzed on the basis of the 2-D small signal model. It shows that it is possible to increase the start oscillation length by tailoring magnetic field's amplitude and its period without changing the synchronous condition of the fundamental wave; in the meantime, when there are two or more azimuthally asymmetric space harmonics in the high power broad-band helix TWT(traveling wave tube), the influences of the Pierce's gain parameter, space charge parameter, and loss parameter on the start oscillation length and real starting asynchronous velocity parameter are also analyzed. Thus the optimum values of the focusing magnetic field, electron beam and helical slow wave
The influence of uniform magnetic field or PPM(periodic permanent magnetic) field on suppressing BWO(back-wave oscillation) is analyzed on the basis of the 2-D small signal model. It shows that it is possible to increase the start oscillation length by tailoring magnetic field's amplitude and its period without changing the synchronous condition of the fundamental wave; in the meantime, when there are two or more azimuthally asymmetric space harmonics in the high power broad-band helix TWT(traveling wave tube), the influences of the Pierce's gain parameter, space charge parameter, and loss parameter on the start oscillation length and real starting asynchronous velocity parameter are also analyzed. Thus the optimum values of the focusing magnetic field, electron beam and helical slow wave
2004,
16.
Abstract:
Applying the mechanics of the propagation of high power microwave in atmosphere and the theory of plasma physics, a sort of new conception antenna-active lens antenna based on plasma is put forward.Its realization is summarized, characteristic parameters such as reflection, transmission, absorption, bandwidth and optimal frequency responding to different function are also analyzed and computed.As a result, this sort of antenna can be used to focus HPM operating waves or reflect transgressive HPM waves on the bass of forming passive filter device.
Applying the mechanics of the propagation of high power microwave in atmosphere and the theory of plasma physics, a sort of new conception antenna-active lens antenna based on plasma is put forward.Its realization is summarized, characteristic parameters such as reflection, transmission, absorption, bandwidth and optimal frequency responding to different function are also analyzed and computed.As a result, this sort of antenna can be used to focus HPM operating waves or reflect transgressive HPM waves on the bass of forming passive filter device.
2004,
16.
Abstract:
To enhance the efficiency of a coaxial-cavity free-electron maser,a method by employing a tapered magnetic field is proposed. Nonlinear simulation indicates that the efficiency of 26.7% measured in the FZK experiment might be enhanced up to 31.5% by a proper taper of the axial magnetic field. The mechanism of the efficiency enhancement is that the tapered magnetic field changes the condition of the electrons' motion and improves the bunching of the electrons in the interaction between the electron beam and the wave.
To enhance the efficiency of a coaxial-cavity free-electron maser,a method by employing a tapered magnetic field is proposed. Nonlinear simulation indicates that the efficiency of 26.7% measured in the FZK experiment might be enhanced up to 31.5% by a proper taper of the axial magnetic field. The mechanism of the efficiency enhancement is that the tapered magnetic field changes the condition of the electrons' motion and improves the bunching of the electrons in the interaction between the electron beam and the wave.
2004,
16.
Abstract:
In this paper, the fuzzy neural network is applied to evaluate the failure thresholds of electronic devices as a function of the parameters of the high power microwave. Based on the characteristic of experimental data, this paper presents a method to evaluate the possibility distribution of electronic device failure applying the possibility theory. Combining the possibility theory and prediction ability of the fuzzy neural network ,the possibility distribution of electronic device failure can be obtained.
In this paper, the fuzzy neural network is applied to evaluate the failure thresholds of electronic devices as a function of the parameters of the high power microwave. Based on the characteristic of experimental data, this paper presents a method to evaluate the possibility distribution of electronic device failure applying the possibility theory. Combining the possibility theory and prediction ability of the fuzzy neural network ,the possibility distribution of electronic device failure can be obtained.
2004,
16.
Abstract:
Compared to FDTD algorithm, pseudospectral time-domain(PSTD) algorithm uses the pseudospectral methods for the spatial derivatives of Maxwell's equations. Simutating large-scale electromagnetic structure, this algorithm improves computative efficiency obviously. But it can't change grid scale smartly because of using FFT. To improve it's application, a new pseudospectral time-domain with non-uniform grid(PSTDNUG) algorithm based on grid transformation is developed. In this paper, the realization of PSTDNUG algorithm and it's application to high power ultra wide-band pulse technology are discussed. The validity of this algorithm is also demonstrated by calculative examples and experiment.
Compared to FDTD algorithm, pseudospectral time-domain(PSTD) algorithm uses the pseudospectral methods for the spatial derivatives of Maxwell's equations. Simutating large-scale electromagnetic structure, this algorithm improves computative efficiency obviously. But it can't change grid scale smartly because of using FFT. To improve it's application, a new pseudospectral time-domain with non-uniform grid(PSTDNUG) algorithm based on grid transformation is developed. In this paper, the realization of PSTDNUG algorithm and it's application to high power ultra wide-band pulse technology are discussed. The validity of this algorithm is also demonstrated by calculative examples and experiment.
2004,
16.
Abstract:
The pre-pulse phenomena are studied by the simple theoretical analysis and the method of electro-circuit simulation in a PFL charging-up by MFCG or capacitors. It is shown that what affect the amplitude of pre-pulse voltage are the grounding inductance and the frequency of the charging loop circuit, which is determined by the secondary coil inductance of transformer and the capacitance of PFL. The parasitical oscillation with high frequency introduced by the grounding inductance doesn't change the peak value of pre-pulse voltage. The frequency of the charging loop circuit is low enough that the peak pre-pulse voltage is only on kV level as PFL is charged through a transformer. The experiments are carried out when the PFL is charged by capacitors through a pulse transformer in two cases tha
The pre-pulse phenomena are studied by the simple theoretical analysis and the method of electro-circuit simulation in a PFL charging-up by MFCG or capacitors. It is shown that what affect the amplitude of pre-pulse voltage are the grounding inductance and the frequency of the charging loop circuit, which is determined by the secondary coil inductance of transformer and the capacitance of PFL. The parasitical oscillation with high frequency introduced by the grounding inductance doesn't change the peak value of pre-pulse voltage. The frequency of the charging loop circuit is low enough that the peak pre-pulse voltage is only on kV level as PFL is charged through a transformer. The experiments are carried out when the PFL is charged by capacitors through a pulse transformer in two cases tha
2004,
16.
Abstract:
This paper describes the generation of the highpower highvoltage pulse on the resistance loads by means of helical explosive magnetic generators (HEMG) at the Institute of Fluid Physics (IFP), CAEP. With the aid of electrically exploded opening switch (EEOS) and transformer, the high voltage 80kV on 100Ω was obtained, and if there is no transformer 400kV on 6Ω resistance load can be obtaied. The pulse width varies from 50ns to 200ns, which is defined by the storage inductance and the resistance load. The rise time is less than 100ns.
This paper describes the generation of the highpower highvoltage pulse on the resistance loads by means of helical explosive magnetic generators (HEMG) at the Institute of Fluid Physics (IFP), CAEP. With the aid of electrically exploded opening switch (EEOS) and transformer, the high voltage 80kV on 100Ω was obtained, and if there is no transformer 400kV on 6Ω resistance load can be obtaied. The pulse width varies from 50ns to 200ns, which is defined by the storage inductance and the resistance load. The rise time is less than 100ns.
2004,
16.
Abstract:
The theory of sine wave klystron and the method to realize it were specified with corresponding equations．With consideration of ns-200 accelerator constitution features main parameters of bunching facility length of bunching tube, equivalent flight length, bunching voltage are decided.by this method, this method was used in designing the bunch apparatus for ns-200 accelerator，bunched pulses of 3.5ns(FWHM) were obtained.Thus the operating mode of nanosecond pulse was achieved.
The theory of sine wave klystron and the method to realize it were specified with corresponding equations．With consideration of ns-200 accelerator constitution features main parameters of bunching facility length of bunching tube, equivalent flight length, bunching voltage are decided.by this method, this method was used in designing the bunch apparatus for ns-200 accelerator，bunched pulses of 3.5ns(FWHM) were obtained.Thus the operating mode of nanosecond pulse was achieved.
2004,
16.
Abstract:
RF phasing system of BEPCⅡ Injector is required to reach the precision of ±2° at the frequency of 2.856GHz. Based on the analysis of elements that affect RF phase for accelerating particles, a general design for this system is presented in this paper, which gives the system structures and its control strategy, reduces the system requirement of ±2° into the feasible parameters of key instruments, and explains even its RF phase measurement. Considering the characteristics of electromagnetic environment of BEPCⅡ injector, as many as possible optic devices and digital measurement technique are introduced to improve the EMC performance of the system.
RF phasing system of BEPCⅡ Injector is required to reach the precision of ±2° at the frequency of 2.856GHz. Based on the analysis of elements that affect RF phase for accelerating particles, a general design for this system is presented in this paper, which gives the system structures and its control strategy, reduces the system requirement of ±2° into the feasible parameters of key instruments, and explains even its RF phase measurement. Considering the characteristics of electromagnetic environment of BEPCⅡ injector, as many as possible optic devices and digital measurement technique are introduced to improve the EMC performance of the system.
2004,
16.
Abstract:
Based on Martin equation, the paper summarizes the calculation method of flashover probability of vacuum insulator stack, which has many insulator stages and large azimuthal transit time, under a given voltage waveform. 1/4 power time dependence and 1/10 power area dependence are chosen in analysis. Then the flashover probabilities of vacuum insulator stack of SATURN and Z machine are calculated as examples. The theoretical criteria for similar vacuum insulator stack design are offered. The paper also detailedly discusses the uncertain factors and existent questions, and establishes the base for further optimizing of the analysis methods.
Based on Martin equation, the paper summarizes the calculation method of flashover probability of vacuum insulator stack, which has many insulator stages and large azimuthal transit time, under a given voltage waveform. 1/4 power time dependence and 1/10 power area dependence are chosen in analysis. Then the flashover probabilities of vacuum insulator stack of SATURN and Z machine are calculated as examples. The theoretical criteria for similar vacuum insulator stack design are offered. The paper also detailedly discusses the uncertain factors and existent questions, and establishes the base for further optimizing of the analysis methods.
2004,
16.
Abstract:
A double pulsed beam generator is built based on 2MeV linear induction accelerator (LIA) injector. The second power source and 8 inductive cells of the injector are divided into two groups and work alternatively. Electron energy of each beam is up to 1MeV and the beam duration is 120ns with adjustable pulse interval (from 200ns to 800ns). The voltage amplitude difference of the two pulses can be less than 2%. The electron beams are emitted from a velvet cathode in a vacuum diode. The beam currents are up to 3kA, measured both by a Faraday cup in anode hole and by a shunt resistor at the rail of the LIA injector. This device can be used to study multi-pulse diode physics and emitting physics of different materials under multi-pulse mode.
A double pulsed beam generator is built based on 2MeV linear induction accelerator (LIA) injector. The second power source and 8 inductive cells of the injector are divided into two groups and work alternatively. Electron energy of each beam is up to 1MeV and the beam duration is 120ns with adjustable pulse interval (from 200ns to 800ns). The voltage amplitude difference of the two pulses can be less than 2%. The electron beams are emitted from a velvet cathode in a vacuum diode. The beam currents are up to 3kA, measured both by a Faraday cup in anode hole and by a shunt resistor at the rail of the LIA injector. This device can be used to study multi-pulse diode physics and emitting physics of different materials under multi-pulse mode.
2004,
16.
Abstract:
This paper presents a microsecond pulse power source with adjusted voltage range (0~120V) and regulative pulse duration (3~14μs), which is used in the measurement of the soft X-ray total energy of high power Z-pinch plasma. By the application of microsecond pulse power source and voltage difference recording method and by the analyses of test circuit, the change of resistance in measurement is considered to be result of the Ni-film bolometer change caused by X-ray irradiation.
This paper presents a microsecond pulse power source with adjusted voltage range (0~120V) and regulative pulse duration (3~14μs), which is used in the measurement of the soft X-ray total energy of high power Z-pinch plasma. By the application of microsecond pulse power source and voltage difference recording method and by the analyses of test circuit, the change of resistance in measurement is considered to be result of the Ni-film bolometer change caused by X-ray irradiation.
2004,
16.
Abstract:
Test beam provides single particle beam for different experimentation. 3 multi-wire proportional chambers were used as detectors to describe single particle track of BEPC (Beijing Electron Positron Collider) test beam. The method of dimensional readout centroids of the charge signals induced on the cathodes of the chamber was discussed. The determination of the charge centroid gives two coordinates in one chamber. Beeline fittings of 3 two coordinates' position paints single particle track accurately. The principle and circuit of charge amplifier、data processing and analysis result was written up.
Test beam provides single particle beam for different experimentation. 3 multi-wire proportional chambers were used as detectors to describe single particle track of BEPC (Beijing Electron Positron Collider) test beam. The method of dimensional readout centroids of the charge signals induced on the cathodes of the chamber was discussed. The determination of the charge centroid gives two coordinates in one chamber. Beeline fittings of 3 two coordinates' position paints single particle track accurately. The principle and circuit of charge amplifier、data processing and analysis result was written up.
